I have a 2005 Ford Mondeo TDCI. battery was dead and the auto shop did not have the exact battery, but close to it (in size and power). Dumb me did not realize that the poles were reversed from what I need and I hooked it up with the wrong polarity. The alternator started smoking quite badly before I realized what was going on (it was dark). Now car appears to be dead, even with correct battery. Fuses appear to be good, but the only light I get on the dashboard is the yellow airbag light + the little red light in the clock is blinking. No dome lights or anything will come on.

1. What could be the issues ? ECU/ Alternator ...?

2. Cost to fix?

I asked a mechanic here and he basically told me to scrap it, if you count mechanics cost against cars worth.

Thanks for your help

- Dynamo

Share this post

Link to post

Share on other sites

well, if the alternator smoked the alternator is likely to be no good, but if you disconnect alternator wires and still the electrics are mostly dead then there is likely much more serious things wrong.

I could easily see it having damaged the ECU and / or the GEM. But it sounds like you could spend money on replacing parts and still find it has damaged more and it could easily become a bottomless money pit

well, if the alternator smoked the alternator is likely to be no good, but if you disconnect alternator wires and still the electrics are mostly dead then there is likely much more serious things wrong.

I could easily see it having damaged the ECU and / or the GEM. But it sounds like you could spend money on replacing parts and still find it has damaged more and it could easily become a bottomless money pit

I think @isetta suggestion to disconnect the wiring from the alternator is a good one, that way if it is shorting out electrically because the alternator is knackered, you're left with the rest of the system which hopefully will work (as a test). If the car is still "dead" after taking this step then it may be that other more expensive things are broken like the ECU/GEM which I suspect wouldn't make financial sense to replace.

Fingers crossed it's just the alternator.

Share this post

Link to post

Share on other sites

there are people on ebay selling ECU/GEM/Key sets but we can't be sure that nothing else has been fried by the reverse battery connections. it might be worth replacing those but it could turn out to be a waste of money and you still have a dead car